Breeding Ecology and Foraging Behaviour of Black-Winged Stilt (Himantopus Himantopus) in Ghana

Abstract

The Black-winged Stilt (Himantopus himantopus) is one of few waterbird species that breeds in wetlands on the coast of Ghana. In recent times, its population has seen an increase on Ghana’s coast while other species are declining. The overall aim of the study was to investigate and document the breeding and foraging ecology of the Black winged Stilt in Ghana. The breeding ecology, diurnal time-activity budget and foraging behaviour of Black-winged Stilts were studied at the Densu Delta Ramsar Site (DDRS). Data were obtained through direct field observations, benthos sampling and video recordings of foraging Black-winged Stilts. Nests were monitored carefully to avoid trampling. A total of 845 eggs from 277 nests were monitored during two breeding seasons. The breeding season in 2016 started in early March and ended in late July, while that of 2017 was from early April till late July. Forty-nine percent (49%) and 59% of nests were successful in 2016 and 2017 respectively. Clutch size ranged from 1-5 eggs and mean incubation period was 23.48 ± 2.88 days. Clutch size was the most important factor influencing nest success and egg hatchability, which suggests that the amount of investment in a nest (number of eggs laid) determines whether or not it will be abandoned. Black-winged Stilts employed aggregation and aggressive displays to ward off predators and chase off other waders in fierce attacks during the peak hatching period. The greatest threats to breeding Black-winged Stilts on the Ghana coast are flooding of nesting sites and egg predation by wandering dogs. Macroinvertebrates in the benthos samples consisted mainly of polychaetes (99%) which occurred at densities ranging from 138 to 1938 individuals /m2. About 86% of all macroinvertebrates in the benthic samples were found in the top 5 cm substrate depth. Blackwinged Stilts fed by pecking, probing, plunging, scything and filtering. Plunging was the most frequently used feeding technique, accounting for 39.0% of all observations, whereas filtering was the least foraging method used accounting for only 1.0% of all observed foraging methods. Pecking (x2=10.743, df=2, p-value=0.0046) and plunging (x2=8.7861, df=2, p-value=0.012) rates differed between the sites, however probing, scything and filtering rates showed no significant difference (p-value > 0.05). Black-winged Stilts spend an estimated 51% of the day time foraging, with 32% successful foraging attempts which varied across the three sites (x2= 27.086, df = 2, p-value = < 0.0001). Foraging site and age influenced foraging rate, while only site influenced intake rate. The findings of this study provide information on the breeding success and foraging behavior of Black-winged Stilt at Densu Delta Ramsar Site. Follow up studies should focus on the link between environmental parameters, prey type and availability, and the population densities of the Black-winged Stilts on the Ghana coast.